Radio tuning apparatus



May 14, 1935. s. TARZIAN RADIO TUNING APPARATUS Filed Feb. 28, 1934 Patented May 14, 1935 UNITED STATES asmo 'rimmo APPARATUS Sarkes Tallinn, Bryn Mawr, Pa., asslgnor to Atwater Kent Manufacturing Company, Philadelphia. Pa.

Fwml'y '28, 1:934, Serial No. 713,267

7 Claims.

jacent range. In the prior art attempts have been made to avoid such reactions by open circumng sections of inductances, by short circulting inductanoes, by loosening of couplings, and by This invention overcomes the dimculties of such reactions by a novel arrangement of circuits and parts as may be best understood by reference to the accompanying figures and specification.

Figure 1 is a simplified circuit diagram of a multi-range tunable radio frequency amplifier and detector employing my invention. v

Figure 2 illustrates a preferred form 01 arrangement of my invention.

Referring to Figure l, the antenna is connected to switch blade I which may be set on switch contact 2, 2', 2", or 2". Eachoi' these contacts successively connect to antenna inductance coils 3, 3, 8", and 8". The antenna inductance coils are each grounded. 'Each 0! the coils has coupled to it a secondary inductance coil; 1. e., 3 is coupled to I, 3' to l, 3" to I". and 8" to 4"". The inductance coils each have connected in parallel individual trimmer capacities 8. 6', 5", and 5". The secondary indudances are grounded at one terminal; the other conmeets to switch points 6, 38", and 6". Switch arm I connects to contact points t, etc. and to the grid of radio frequency vacuum tube t; The switch blade is also connected to the stator plates of the main variable tuning condenser C1. The motor plates are grounded. The cathode of tube 8 is grounded through resistor II which is by passed by fixed condenser 10.

The plate oi! tube 8 connects to switch blade H which contacts points l2, l2, lI",or 12". These switch points are connected to the primary inductances l3, I3, 13', and IS'. The remaining terminal of the inductances connects to +3 of the plate battery which is illustrated at ll and by passed by fixed condenser 15. Each of primaries 13 to W is coupled respectively to secondary inductances it, Hi, It", and IB. The secondary inductances are grounded at one terminal and are shunted by individual trimmer capacities H, H, H", and 11'. The high potential terminal of each secondary inductance connects respectively to switch points It, i8, i8", and ll'. Switch arm 19 contacts switch points it etc. and is also connected to main tuning condenser C2 and grid condenser 20. The grid condenser connects switch arm I! and the grid of the. I

vacuum tube detector 2|. The grid is grounded through grid leak 22. The cathode of tube 2| is grounded. The plate of this tube connects to telephone receivers 23 which are by passed by fixed condenser 24. The telephone receiver circuit is completed through B-battery I4, which has its negative terminal grounded. In place of telephone receivers a vacuum tube amplifier may be employed.

For the sake of simplicity the battery to heat the filament circuits of tubes 8 and 2| is omitted. Description of the filament circuit is unnecessary, being well known to those skilled in the art.

The enclosed dotted lines of Figure 1 represent shields which house the radio frequency transformer systems. Each shield is grounded. S1 houses 3, l, 5, and 3, 4, 5. S2 houses 3", 4", 5", and 3, 4", 5". S3 houses l3, l6, l1, and l3, 16', H. S4 houses 13'', I6", 11", and l3, '6!!! '1III The operation of the system with the switch arms i, l, H, and I! on the uppermost contacts is the well known, conventional tunable radio frequency amplifier and detector. Each successive position of the switch arms, which for convenience may be linked together by insulated coupling arrangements 25, results in a different tunable frequency range. By way of example:-

Switch contact Tunable range Inductances Microhmries 2, 6, 12, i8 220 1! on 1/ 5 2', 6', 12', 18' 5 2, 6"' 12', 18'" 1 Unless precautions are taken the natural frequency of a lower frequency range will lie within the next adjacent range causing undesirable reaction. This resulting reaction may best be expressed by the equation VliK where f =resu1ting frequency, f1=frequency of one tuned circuit, f2=frequency of other tuned circuit, K=coefilcient of coupling. An examination of the equation will show that the further apart the frequency of the two circuits and the less the coupling, the less each will react on the other.

I propose to minimize this reaction by the arrangement shown in Figures 1 and 2. S1 and S2 represent shielded grounded containers of copper or other suitable metal. P1 and P2 represent insulated coil forms, 4 represents the secondary inductance of lattice winding type of the range 540 to 1600 kilocycles. 4' is the inductance of range 4000 to 10,500 kilocycles. 4 is the inductance of range 1600 to 4000 kilocycles, and 4 the inductance of range 10,500 to 20,000 kilocycles.

With this arrangement the natural frequency of inductance 4 and capacity 5 (including stray capacities) is sufficiently removed from the low freequency limit of 4, 5, and 01, so that in spite of the coupling between 4 and 4', which is the result of relatively close windings on the common form P1, undesirable reaction is substantially eliminated. In a similar manner 4 and capacity 5" (including stray capacities) will not have a natural frequency which will be near the low frequency range of 4, 5", and C1. Since the circuits within S1 are shielded from the circuits within S2, there can be no mutual reactions between these circuits. It should be understood that a single shield S1 may be used to prevent reactions from circuits having adjacent or overlapping frequency ranges.

Thus it becomes possible to avoid undesirable reactions between tuned circuits of used and unused ranges without attempting extreme looseness of coupling which requires spacing beyond the limits of a compact receiver, or pluralities of separate shields and coil forms. By this novel arrangement of circuits and frequency ranges, I have for-11d that two coil forms and one shield may replace four coil forms and four shields with great resulting savings of expense and space.

The same treatment of the tuned circuits of the detector will be used with the same resulting saving and efficiency of operation. It will be understood that the variable condensers C1 and 02 may be ganged together and that the individual trimmers on each tuned circuit are adjusted to permit single dial operation and also to prevent undesirable reactions from overlapping tuning ranges. In the event that a superheterodyne cirsuit is used, my invention may be employed in the various tunable circuits, including the oscillator circuits.

I claim:

1. In a multi-range radio frequency tuning system, the combination of a plurality of circuits, comprising inductances and capacities, said inductances being of substantially different values, said capacities permanently connected in parallel to said inductances, the maximum frequency of each of said circuits being substantially different, means for providing mutual coupling between two circuits of said plurality used in non-overlapping frequency ranges means for substantially eliminating coupling between circuits used in overlapping frequency ranges, a variable capacity, and means for successively connecting said variable capacity to each of said circuits.

2. In a multi-range radio frequency tuning system, the combination of a plurality of circuits, comprising inductances and capacities, said inductances being of substantially different values,

said capacities permanently connected in parallel to said inductances, the maximum frequency of each of said circuits being substantially different, means for providing mutual coupling between two circuits of said plurality used in non-overlapping frequency ranges, a variable capacity, means for successively connecting said variable capacity to each of said circuits and means for minimizing coupling between circuits of said plurality used in overlapping frequency ranges, whereby undesirable reactions are avoided.

3. In a multi-range radio frequency tuning system,.the combination of a plurality of inductances of different values, means for providing mutual coupling between said inductances used in non-adjacent frequency ranges, means insuring substantially zero coupling between said inductances used in adjacent frequency ranges, and a variable capacity connected to one of said inductances for tuning over a range of frequencies, whereby undesirable reactions are avoided.

4. In a. multi-range radio frequency tuning system, the combination of a plurality of inductances of different values, trimmer capacities connected in parallel to each of said inductances, means insuring substantially zero coupling between pairs of said inductances and capacities used in adjacent frequency ranges, means for providing mutual coupling between pairs of said inductances and capacities used in non-adjacent tween said inductances, separate adjustable capacities permanently connected in parallel to said inductances, the circuits comprising said inductances and capacities being used in non-adjacent ranges, another circuit of inductance and capacity for use in frequency ranges adjacent to the frequency ranges employing the first mentioned circuits, means insuring substantially zero coupling between circuits of adjacent ranges, and

. r means for successively connectmg 8, variable 08- pacity to each of said circuits for tuning through a range of frequencies.

6. In a multi-range radio frequency tuning system, the combination of a plurality of inductances, means substantially eliminating coupling between said inductances used in adjacent frequency ranges, means for providing mutual coupling between said inductances used in non-adjacent frequency ranges, and a variable capacity selectively connected to one of said inductances for tuning through a range of frequencies.

'7. In a multi-range radio frequency tuning system, the combination of a plurality of inductances, trimmer capacities connected in shunt to said inductances, means substantially eliminating coupling between said inductances used in adjacent frequency ranges, means for providing mutual coupling between said inductances used in non-adjacent frequency ranges, and means for tuning any one of said inductances through a range of frequencies.

SARKES TARZIAN. 

